Bathroom Sink Pipe Assembly
There is a pipe from the drain that is a "Slip" type of joint. It slides inside of another pipe. I'm having problems getting it to be water tight and not leak. What am I not doing right? Is it the size of pipe that is the problem? Do I need a special part?
Am I making any sense what so ever? LOL

From reading some other posts. It is the tail pipe that slides into the "J-Pipe" I think that is the right terms? It is metal.

This sounds like a simple case of a 1 1/4" lavatory tail piece going into a 1 1/2" trap raiser. The problem is that you have a 1 1/2" nylon washer in the compression fitting when you should be using a 1 1/2 X 1 1/4" nylon washer.
Pick one up from a plumbing shop for a few pennys and your troubles are over. Good luck, Tom